CELLULAR STRUCTURE 33 
veloped by the swelling jelly, and they may 
even entirely disappear. ‘The cell colonies 
thus consist of motionless masses of green 
jelly. But there is as yet very little organisa- 
tion in such colonies. The form of the mass 
is not constant, and a return to what may be 
termed normal conditions of life may readily 
lead to a complete disruption of the colony, 
the individual cells escaping from the jelly 
and returning to the unicellular motile condi- 
tion which is in the main characteristic of this 
group of alge. 
This tendency to form agglomerations of in- 
dividual cells is carried to a far greater degree 
of perfection in some other groups of the lower 
alee. Thus Apiocystis Brauniana (Fig. 2), 
an alga fairly often to be met with in ponds, 
attached to larger alge and other objects, 
consists of a pear-shaped mass of jelly in 
which are scattered masses of chlorophyll- 
containing protoplasm. The little proto- 
plasmic spheres, which represent the living 
part of the individual cells composing the 
Apiocystis plant, are grouped in the more 
peripheral parts of the gelatinous matrix 
formed by the swelling of the common cell 
walls. Each cell (see footnote on p. 20) is 
furnished, like Chlamydomonas, with a pair 
of cilia, but these have ceased to be functional, 
for they are enclosed in a thin projection 
of the gelatinous wall. When examined 
attentively, it can be observed that the 
individual cells, or protoplasts, are multiplying 
Cc 
